Emergency department visits for acute gastrointestinal illness after a major water pipe break in 2010
BACKGROUND: When a water pipe breaks, contaminants can enter the drinking water system and cause waterborne illnesses such as acute gastrointestinal illness (AGI). In May 2010, a major water pipe broke near Boston, Massachusetts, and a boil water order was issued to nearly two million residents.
OBJECTIVE: The objective of this paper was to assess the association between the major water pipe break in Boston, Massachusetts in 2010 and subsequent emergency department (ED) visits for AGI. The hypothesis was that residents living in communities affected by the pipe break would be at an increased risk for AGI during the week following the break.
METHODS: A case-crossover study design was used to examine the association of interest. Residents in the Boston area were considered exposed and at risk for AGI during the week following the water pipe break. Cases were identified from electronic ED records, with AGI defined based on ICD-9-CM diagnosis codes. Control dates were selected two weeks before and two weeks after the case date. Conditional logistic regression models were used to estimate the risk of visiting the ED for AGI following the pipe break. A separate analysis also considered a negative control exposure by examining the same association among residents of communities unaffected by the pipe break.
RESULTS: Among residents affected by the water pipe break, there were 1,818 ED visits for AGI during a 64-day study period around the time of the break. Overall, there was a 32% increased odds for visiting the ED for AGI during the 0-3 days after the pipe break (Odds Ratio, OR=1.32; 95% Confidence Interval, CI: 1.07-1.61). This association was slightly attenuated during the 4-7 day hazard period (OR=1.17; 95% CI: 0.93-1.47). When the analysis was stratified by age group, young children (OR=1.40; 95% CI: 0.99- 1.99) and youth/adolescents (OR=1.59; 95% CI: 0.99-2.55) were at a somewhat higher risk of AGI in the 0-3 days after the pipe break. Also, communities less than 12 miles from the break were at increased odds of illness during the 0-3 day hazard period (OR=1.46; 95% CI: 1.15-1.84). In a separate analysis using a negative control exposure, there was no association between the pipe break and AGI.
CONCLUSION: This study found an association between a major water pipe break and ED visits for AGI, particularly during the 0-3 days after the break, when a boil water order was in effect. The lack of association with the negative control exposure provided further confirmation of the validity of this association. As drinking water infrastructure ages and the occurrence of pipe breaks continues to rise, it is important to consider the related health consequences.